1. Field of the Invention
The present invention relates to a scanning method by using a sheet feed scanner. More specifically, the present invention relates to a scanning method with improved resolution by using a sheet feed scanner.
2. Description of the Related Art
As the operation performance of computers increases, and the Internet and multimedia are widely used, more image input devices such as digital cameras and optical scanners are increasingly required. Different from digital cameras that directly output the digital data of the image, the optical scanners have to transform analog data of the image into digital signals before the data is transmitted to the computer. According to the input of the document image, the optical scanners can be divided into pocket scanners, sheet feed scanners, drum scanners, and flatbed scanners. A sheet feed scanner manufactured by contemporary technology has 600 dpi of optical resolution with a contact image sensor (CIS).
FIG. 1, is a schematic view of a conventional sheet feed scanner. The sheet feed scanner 100 includes a sheet feeder 110, and a scan module 130. The sheet feed scanner 110 serves to convey a paper sheet 150. The scan module 130 scans the sheet paper 150 conveyed from the sheet feeder 110. The sheet feeder 110 includes a conveying guide 112, a plurality of rollers 114 and a scanning window 116. The sheet paper 150 is conveyed along the conveying guide 112. The rollers 114 are arranged on the conveying guide 112, with two of the rollers 114 rolling in contact with each other so that the paper sheet 150 can be transmitted by the rollers to pass between the two rollers 114 and go forward. When a motor (not shown) drives the rollers 114 to rotate, the rollers 114 convey the paper sheet 150 in a moving direction 120. An axis 115 of each of the rollers 114 is perpendicular to the moving direction 120 of the paper sheet 150. Furthermore, a scanning window 116 is arranged under the sheet feeder 110. The scanning module 130 includes a stationary scanning head 132 that is fixed in the scan module 130. The stationary scanning head 132 scans the paper sheet 150, which is conveyed from the sheet feeder 110, through the scanning window 116 of the sheet feeder 110.
In the above sheet feed scanner 100, the stationary scanning head 132 scans the paper sheet 150 when the paper sheet 150 is located above the scanning window 116. The scan resolution is determined on moving the paper sheet 150 by the motor and the rollers 114. The scan resolution thus obtained by such a sheet feeder 100 is low.